A back-light device to radiate light to the back of a transmission-type liquid-crystal panel is available (patent literature 1), wherein light is radiated from the light-radiating surfaces of LED light sources, enters a light-guiding plate through its incident surface, and is diffused in the light-guiding plate and directed to the back of the liquid-crystal panel.
The back-light device comprises (i) a printed circuit board on which the LED light sources are installed, (ii) the light-guiding plate, (iii) optical sheets which are disposed on one side of the light-guiding plate and direct the light to the back of the liquid-crystal panel, (iv) a reflecting sheet which is disposed on the other side of the light-guiding plate and reflects light toward the liquid-crystal panel, and (v) a frame which houses and holds the above components.
Patent literature 1: Japanese Unexamined Patent Publication No. 2002-75038
The above back-light device has the following problems.    (1) A gap may be left between the light-radiating surfaces of the LED light sources and the incident surface of the light-guiding plate because of assembly errors and parts errors. In this case, it is difficult to guide the light from the light-radiating surfaces to the incident surface efficiently.    (2) It is difficult to dissipate the heat of the LED light sources; accordingly, it is difficult to feed an electric current of high intensity to the light sources.    (3) If the frame is grounded, or earthed, an insulating member has to be provided between the frame and the printed circuit board to insulate the electronic parts installed on the printed circuit board from the frame. The insulating member increases the cost of the back-light device.
Under the circumstances, it is an object of the present invention to provide a back-light device and a liquid crystal display whose manufacturing costs are low and wherein the light from light sources is guided to a light-guiding plate and the heat of light sources is dissipated efficiently.
It is another object of the present invention to provided a back-light device and a liquid crystal display whose manufacturing costs are low and wherein the electronic parts are efficiently insulated from the frame.